A portable circular saw comprises a circular saw blade, a motor to drive the blade, typically through reduction gearing, a support structure, a handle, a blade guard, and a foot or footplate. The footplate is typically either a drop foot or a pivot foot, either of which is designed to rest on a surface that is being cut, and is made to move to adjust the depth of cut and provide support for the motor and blade. A drop foot moves essentially parallel to itself and generally perpendicular to the axis of rotation of the saw blade and is often arranged to rotate with respect to a cut line to allow the saw to cut at an angle other than perpendicular to the surface of a workpiece. A pivot foot is constructed to rotate about two axes, one that is parallel to the axis of the saw blade to allow selection of the depth of cut and one that is contained in a plane perpendicular to the axis of the saw blade to allow selection of the angle of cut. The foot supports the portable circular saw on the surface of a workpiece to cut at an angle that may be other than perpendicular to the surface.
Portable circular saws are typically made in two styles. One style, called sidewinder, parallel shaft or simply circular saw, has an electric motor that is placed with its shaft parallel to the axis of rotation of a circular saw blade, so that the motor speed is reduced by a set of spur gears, typically, although not necessarily, helical spur gears. The other style of portable circular saw, called a worm drive circular saw, or more recently a hypoid gear variation thereof, has an electric motor that is placed with its shaft in a plane perpendicular to the axis of rotation of the saw blade, so that the speed reduction is produced by a set of worm gears or a hypoid gear set. For either the sidewinder or the worm drive, saw cuts at an angle to the surface of the material being cut are guided by a foot such as those described above. The saw is rotated about front and rear pivot points on an axis parallel to the cut that is to be made and at an angle determined by a setting of the blade with respect to the foot. Pivotal movement of the motor and blade can also take place about a hinge having an axis parallel to the axis of the rotation of the saw blade. The hinge may be associated with either the front or rear pivot. This pivotal movement is effected in a direction so that the motor is raised from or lowered to the surface of the material being cut. The motor is rotatably adjustable about the front and rear pivot points with respect to the foot and is typically adjustable continuously up to an angle of 45.degree., since cuts at angles greater than 45.degree. have had to be made by cutting the workpiece while tilting the saw or the workpiece. This is very dangerous and is not recommended. The foot has a quadrant that is usually marked at angles of 0, 15, 30 and 45 degrees and is often fixed with detents to mark these angles for increased convenience in angle cutting.
It may be desirable to make a cut with a portable circular saw at an angle as great as 60.degree. to the surface of a workpiece. This would be especially likely in cutting what is often referred to as "two-by" or "2X" lumber in a single cut and would be very advantageous. This would be an advantage in that it would increase efficiency in general carpentry and in particular in framing work, which is a specialized branch of carpentry devoted to erecting wooden frames for structures.
An important safety feature that is generally required on portable circular saws is a blade guard that covers the blade when the saw is not in use and that includes a lower guard cover that rotates about the axis of the saw blade to uncover the teeth of the blade when a cut is being made. When a bevel cut is being started perpendicular to the edge of a board, the blade cover is typically pushed out of position automatically as an operator advances the saw and starts the cut. Normally, when a bevel cut is being started at an angle to the edge of a board, the operator must operate a lever manually to rotate the blade cover out of the way to let the blade make contact with the board. Any rotation of the motor and blade with respect to the foot to allow a cut at an angle other than perpendicular to the surface of a workpiece must provide for proper operation of the moveable lower blade guard so that the blade is covered when the saw is not in use and is retracted to permit a cut when the saw is placed in position to cut on a workpiece.
The improved portable circular saw disclosed herein permits rotation of the saw blade up to an angle of 60.degree. from the vertical with respect to the foot and the surface of the workpiece. This permits the cutting of lumber having a 2-inch nominal dimension in a single cut at 60.degree.. The improved saw provides for operation of the lower blade guard at any angle to which the blade can be set and at any initial angle of cut with respect to the edge of a workpiece.
Thus it is an object of the present invention to provide a portable circular saw that will cut through 2X lumber or other material at an angle of 60.degree. from the vertical.
It is another object of the present invention to provide a circular saw that will protect the user with a lower blade guard that covers the lower portion of the blade when the saw blade and motor are at an angle of 60.degree. with respect to the footplate and the saw is not being used.
It is still another object of the present invention to provide a portable circular saw that will cut through 2X lumber at an angle of 60.degree. and which is mounted on a foot that is of substantially standard size and which has sufficient strength to provide a safe mounting platform for the motor and saw blade.
It is yet another object of the present invention to provide a circular saw that will cut through 2X lumber or other material at an angle of 60.degree. from the vertical by utilizing a change in depth of cut or blade elevation in conjunction with the angle of blade rotation to achieve the 60.degree. cut.
It is also an object of the present invention to provide a positive stop at 45.degree. that has a manual override to allow the saw to continue to pivot to 60.degree..
Other objects will become apparent in the course of the detailed description of the invention.